(1) Field of the Invention
The present invention relates to an electrically conductive fulvalene derivative represented by formula (1) below. ##STR2## where A.sup.1 -A.sup.8 are at least one atom or a combination of two or more atoms selected from S atom, Se atom, and Te atom; and R.sup.1 -R.sup.4 are alkyl or alkene having 3 to 22 carbon atoms.
(2) Description of the Related Art
Organic substances are typical electrical insulators, but there are two methods of rendering them electrically conductive. One method utilizes the mobility of .pi.-electron among the electrons which one carbon atom possesses. According to this method, the .pi.-electron cloud of a carbon atom is caused to overlap with another between molecules. An example is a polycyclic aromatic compound. Graphite and carbon black are also electrically conductive because of the mobility of the .pi.-electron they have.
The other method utilizes the charge transfer force among organic molecules. Electrons can be transferred in an organic solid when the electron donating property and the electron accepting property, which are the real nature of organic substances, are combined alternately. A typical example is a charge-transfer simple salt or complex composed of tetrathiofulvalene (TTF), which is an electron donor, and tetracyanoquinodimethane (TCNQ), which is an electron acceptor. Because of this method, there appeared synthetic metals and superconducting organic substances which are electrically conductive like metals although they are organic.
The compounds of this kind include the one having such structure that the S atoms in the TTF skeleton are substituted entirely or partly by Se atoms or Te atoms. It also functions as an electron donor like TTF and forms a synthetic metal or superconducting organic substance.